What if the MTA’s bid to float bonds to cover new projects like the Second Avenue Subway fails again? Experts think 30 percent of the vote on Election Day, statewide, will have to come from New York City for the act to pass, since everyone upstate will vote against it. “We’re concerned about the fact that if the Mayor is so far ahead, maybe people won’t come out to vote, period,” A.J. Castelbuono, who spent $3 million on the last failed bond-act measure, told Matthew Schuerman.